In many applications, fasteners used to secure an assemblage of components, must be locked to prevent inadvertent loosening or separation. For example, in the aircraft industry, bolts used to hold critical components are fixed with a locking wire to prevent loosening due to vibration or other factors. For many military products, the Government requires the use of locking wires for the same reason.
In a typical application, each fastener includes an aperture for receiving the locking wire. After the fastener or group of fasteners is installed, the wire is passed through the aperture of one or more fasteners and the ends of the wire are twisted to secure it into position. In many cases, the twisting must be carried out in a careful manner to insure that the wire is not unduly stressed but yet is tightly installed so that loosening of the fastener is inhibited.
To facilitate the installation of locking wire, various tools have been proposed. One such tool comprises a pair of movable jaws, a means for locking the jaws in a closed or clamped position and a drive mechanism for rotating the jaws to effect the twisting of the wire ends. In a commonly available version of this tool, the tool is plier-like in construction and includes jaws that are opened and closed by the operator by means of handles. The drive mechanism is carried by at least one of the handles and includes a housing that rigidly mounts a nut-like element. The nut-like element is designed to engage a twisted rod mounted for reciprocating movement within the housing. An operating knob is operatively connected to one end of the shaft. In use, the operator clamps the wire to be twisted between the jaws. A jaw locking mechanism is engaged to maintain the clamped position of the jaws. The operating knob connected to the end of the shaft is then pulled by the operator. As the shaft passes through the drive nut, rotation is imparted to the housing which causes the entire tool including the jaws to rotate about an axis defined by the twisted rod. This rotation rotates the jaws a predetermined number of turns to effect twisting of the wire. After the wire has been twisted, the jaws are released to unclamp the wire ends.
It has been found that the drive mechanism bears the brunt of the wear in the tool. Although the twisted rod and/or the nut element is replaceable in some tools, it has been found that replacement is not easily effected and/or the construction is prohibitively expensive.
The use of locking wire is not limited to aircraft and/or military applications. The medical profession, specifically orthopedics, uses wire in the setting of bones or the like. As a result, a wire twisting tool suitable for the surgical environment is desirable. In order to satisfy this need, the tool must lend itself to sterilization. It is believed that prior wire twisting tools were difficult or impossible to completely sterilize and hence were unacceptable for use by medical professionals.